It might be a bit surprising for an MMO player, but TESO's quest system is essentially exploration-based. Thus, no need to look for what is traditionally called quest "hubs", that is to say camps or cities where we find all the quest givers who will cause us to go back and forth between this hub and the places where the quests take place. The main quest is not a common thread that will take us from hub to hub, so don't count on it to move forward and discover new ways to progress.
Before leaving an important city, still remember to collect the quests related to the guilds of mages and warriors. It will embroil you in fascinating stories that it would be a shame to miss.
Apart from this exception, leave the beaten track and go for the adventure. As long as you stay in an area corresponding to your level, it will be fine. Visit strange places, caves, abandoned houses and be vigilant. There might be a quest to find there. Observe the environment well and do not go straight ahead: an NPC may appear to ask for help. It would be a shame to miss it and ignore it like a prince!
If at some point you run out of quests, don't panic, the map is here to help. All markers point to important stuff, chances are there are quests nearby. The most important are the bigger symbols, like the black tree below the quest area where I am. Hovering the mouse over it tells me that I must uncover the dark secrets of the harfreuse swamp. I'm on it, the area still deserves my attention, the symbol is black.
On the other hand, when I have completed the quests in an area, having solved a mystery or helped all the people who asked for it, then the icon turns white. If we hover the mouse over it, we then have a summary of what happened there. Here at the highest tree level, I lifted Angof's corruption and saved the Wyrd tree.
TESO offers a new way to complete quests without the hassle. We go where we want. We do what we want. Without the main quest line, it's entirely possible to just not complete a quest that you don't like and explore further. We won't be stuck.
Just note that some quests have consequences. If you have started the adventure, you will undoubtedly have met some characters from the beginning. So, inevitably, if you do not complete certain quests, future events may never happen ... or at least differently!